Dark Is the Sun

Fifteen billion years from now, Earth is a dying planet, its skies darkened by the ashes of burned-out galaxies, its molten core long cooled. The sunless planet is nearing the day of final gravitational collapse in the surrounding galaxy. Mutations and evolution have led to a great disparity of life-forms, while civilization has resorted to the primitive.
Young Deyv of the Turtle Tribe knew nothing...